The long-term goal of this technology development project is improve the rehabilitation of veterans suffering from lung diseases through the development of the first truly portable, biocompatible, artificial lung capable of short and long term respiratory support. Artificial lungs are currently used to rehabilitate lung disease patients; however, significant advances in gas exchange, biocompatibility, and portability are required to fully realize their potential. Microfluidic artificial lungs promise to enable a new class of truly portable artificial lungs through feature sizes and blood channel designs that more closely mimic those found in their natural counterpart. Our small-scale microfluidic artificial lungs achieved the highest gas exchange efficiency of any artificial lung to date. Their lifetimes were significantly improved through the application of biocompatible surface coatings. Initial in vivo demonstrations were performed in an animal (rat) model. However, current microfabrication techniques limit the microfluidic networks in these devices to two dimensions, thereby severely limiting potential device topologies and resulting in inefficient blood distribution networks. Further, current construction techniques may not be suitable for the large area production required for human applications. In this study, we will for the first time harness high resolution 3D polymer printing technology to create large area microfluidic lungs with truly three dimensional blood flow networks and topologies. Constructed 3D printed microfluidic artificial lungs will exhibit gas exchange suitable for some human applications, while using a fraction of the blood contacting surface area, blood volume, and total volume of current commercial devices. The objectives of the current technology-development SPiRE proposal are thus to: 1) Determine optimal 3D printing parameters for microfluidic artificial lungs; and, 2) Construct and test the first 3D printed microfluidic artificial lung in the laboratory using whole animal blood. At the conclusion of this study, we will be ready to test our 3D printed microfluidic artificial lungs in a large animal model. The listed objectives are thus critical to advancing this promising technology towards initial acute systems for veteran pulmonary rehabilitation.